WTF Are Fourth-Generation Biofuels?

Have biofuels been around long enough for there to be four generations of them? Those in the biofuel industry think so. Scientists at the University of Essex have discovered a new mechanism that regulates the process of carbon fixation in plants. The research, to be published today in the Proceedings of the National Academy of Sciences, could lead to improvements in so-called “fourth-generation” biofuels by letting scientists design feedstocks that capture more carbon (hat tip to Biopact).

There’s been a great deal of debate recently over first-generation, or food-based, biofuels. Meanwhile, a breakthrough to commercialize second-generation, or lignocellulosic, biofuels has yet to materialize. So how are we already jumping to the fourth generation? We’ve broken down their evolution below, including making note of any related startups.

First Generation:
First-generation biofuels rely on food crops as their feedstock. Corn, soy, palm and sugarcane all have readily accessible sugars, starches and oils. So brewing them into biofeuls simply involves either fermenting the sugars or chopping up the fatty oils through transesterfication.

Most biofuel startups are not working with first-generation feedstocks but biofuel distribution startups, such as Propel Biofuels and Conserv Fuel, are working almost exclusively with food-based biofuels because that’s all that’s currently available.

Second Generation:
Second-generation biofuels use lignocellulosic biomass as feedstock, among them dedicated biofuel crops like switchgrass and agricultural residue such as corn stalks. Using specially designed microorganisms, the feedstock’s tough cellulose is broken down into sugar and then fermented. Alternatively, a thermochemical route can be taken whereby the biomass is gasified and then liquefied, a process known as “biomass-to-liquid.”

A lot of venture funding is going into second-generation biofuels startups as they race to develop a single, cost-effective process for producing biofuels. Kior is working on their “biomass catalytic cracking process” while Coskata claims they can produce ethanol for $1 a gallon using old tires as a feedstock. Mascoma is working to build a “super bug” that would digest lignocellulosic feedstocks while ZeaChem plans to tap poplar trees for fuel.

Third Generation:
Rather than improving the fuel-making process, third-generation biofuels seek to improve the feedstock. Designing oilier crops, for example, could greatly boost yield. Scientists have designed poplar trees with lower lignin content to make them easier to process. Researchers have already mapped the genomes of sorghum and corn, which may allow genetic agronomists to tweak the genes controlling oil production.

Monsanto and ADM have been developing genetically modified cultivars for years but amid intense competition and anti-GMO criticism are usually mum about their research. Arborgen is a startup working to make trees by design for biofuel and timber purposes.

Fourth Generation:
Fourth-generation technology combines genetically optimized feedstocks, which are designed to capture large amounts of carbon, with genomically synthesized microbes, which are made to efficiently make fuels. Key to the process is the capture and sequestration of CO2, a process that renders fourth-generation biofuels a carbon negative source of fuel. However, the weak link is carbon capture and sequestration technology, which continues to elude the coal industry.

Venter says his Synthetic Genomics can make moot the issue of CO2 capture. His company plans to combine the processes of feedstock growth and fuel processing by designing organisms that will inhale CO2 and excrete sugars. We’ll see if these potentially world-saving bugs become a reality in the next 18 months.